1. Field of the Invention
The present invention relates an improved process for producing methanesulfonyl fluoride useful as an intermediate in the production of medicaments or agricultural chemicals or as a starting material in the production of trifluoromethanesulphonic acid (CF.sub.3 SO.sub.3 H).
2. Related Background Art
Trifluoromethanesulphonic acid is generally produced by means of the electrochemical fluorination technique, wherein the use of methanesulphonyl fluoride as the starting material is more advantageous in comparison with the case of using methanesulphonyl chloride (CH.sub.3 SO.sub.2 Cl) as the starting material in that an improved yield can be attained with good current efficiency and without occurrence of chlorine gas.
Methanesulphonyl fluoride (CH.sub.3 SO.sub.2 F) is generally produced in the following manner. That is, a metal fluoride such as potassium fluoride (KF) is mixed with methanesulphonyl chloride (CH.sub.3 SO.sub.2 Cl), followed by reaction in the presence of a solvent such as water. (see, J. Chem. Soc. p. 178 (1956))
The reaction herein can be expressed by the following formula. EQU CH.sub.3 SO.sub.2 Cl+KF.fwdarw.CH.sub.3 SO.sub.2 F+KCl
After the reaction has been completed, the resultant reaction product is subjected to distillation or filtration to separate methanesulphonyl fluoride (CH.sub.3 SO.sub.2 F) as the final product.
The above reaction is usually conducted while controlling the water content in the reaction system to a minimum with a due care about the reaction rate, because the methanesulphonyl chloride as the starting material has a property of being hydrolyzed, and the methanesulphonyl fluoride as the final product has a property of being hydrolyzed and also a property of being somewhat dissolved in water. In view of this, in the case of separating the methanesulphonyl fluoride from the reaction product obtained in the above reaction by means of the distillation manner, it is difficult to attain a desirably high yield.
As above described, it is possible to separate the methanesulphonyl fluoride from the reaction product obtained in the above reaction by means of the filtration method. However, disadvantages occur in this case such that the filtrate unavoidably contains by-products such as salts in addition to water and because of this, the successive purification process eventually become complicated.